Ballast for gaseous discharge devices



Dec. 11, 1956 A. E. FEINBERG ETAL 2,774,011

BALLAST FOR GASEOUS DISCHARGE DEVICES Filed Feb. 23, 1952 2 Sheets-Sheet l mmgg I 1956 A. E. FEINBERG ET AL 2,774,011

BALLAST FOR GASEOUS DISCHARGE DEVICES Filed Feb. 23, 1952 2 Sheets-Sheet 2 United States Patent BALLAST FOR GASEOUS DISCHARGE DEVICES Albert E. Feinberg and Frank S. Endo, Chicago, 111., as-

signors to Advance Transformer Co., Chicago, 111., a corporation of Illinois Application February 23, 1952, Serial No. 273,111

6 Claims. (Cl. 315-438) This invention relates to a ballast for igniting and thereafter providing the operating voltage for a plurality of gaseous discharge devices. Specifically the invention is concerned with the construction of the core for such apparatus, and the apparatus is especially intended for use with two gaseous discharge devices.

It often becomes necessary to provide for the ballasting of two gaseous discharge devices which are of different characteristics. Thus, for example, Where the gaseous discharge devices are of different starting voltages, two ballasts are required. The invention herein is especially intended, and one of the principal objects thereof is, to provide a single ballast which will ignite and thereafter provide operating voltages for a pair of gaseous discharge devices of diiferent characteristics.

In connection with the above object, it is also desired to provide a ballast which is extremely small, efiicient, and economical.

Other objects of the invention lie in the provision of a novel core construction whereby the gaps required in the core are maintained constant and quiet; a construction providing an elongate shell-like unitary core having a central winding leg adapted to be wedged into a permanent position and provide uniform, efficient, and desirable magnetic characteristics.

Additional object lies in the provision of an electromagnetic device having a transformer and choke associated therewith but utilizing less iron than would be required were the choke and transformer separately formed.

Still a further object of the invention is to provide a novel ballast construction in which, through the medium of appropriate arrangement of the voltage senses of the various windings, certain parts of the core of the said ballast may be made considerably smaller than heretofore deemed possible at no expense to the electrical characteristics of the apparatus and without the danger of saturation effects in the core.

Many other objects will become apparent as the description of the invention proceeds, and many advantages will be brought out with the complete description and explanation of a preferred embodiment. This embodiment and various modifications thereof are illustrated in maximum light, same being the type of gaseous discharge devices adapted to be used with the invention.

Fig. 3 is a schematic electrical circuit of the ballast showing the manner in which the gaseous discharge devices are connected therewith to complete the circuits thereof.

Figs. 4 and 5 are fragmentary views similar to that i 150 volts and operates at about 83 volts. Since the 2,774,011 Patented Dec. 11, 1956 Such occasions may arise in connection with other than fluorescent lamps, but in this case fluorescent lamps will be discussed by way of example.

Recently, the use of fluorescent lamps for lighting has attained wide-spread popularity, especially in the illumination of homes and apartments. For this purpose there have been developed circular tubes capable of being associated with compact lighting fixtures, multiple fluorescent lamp fixtures had posed problems with respect to lighting efficiency, for, Where circular lamps of identical dimension are positioned coaxially, the lower lamp masks the upper. Obviously it is impractical to dispose the lamps with their axes parallel or horizontal. Thus, fixtures were constructed for use with two such circular lamps, but with the lamps one inside of the other whereby to achieve maximum downward illumination. The lamps are arranged coaxially, but in the same plane.

Obviously this can only be done with lamps of different diameters and hence different lengths. Since fluorescent lamps depend upon their dimensionsfor their char acteristics such arrangement resulted in the bringing together in one fixture of two gaseous discharge devices of different characteristics.

Such an arrangement is shown in Fig. 2. There is illustrated inner circular fluorescent lamp 10 of lower starting voltage than an outer circular fluorescent lamp 11. These can be arranged concentrically in a fixture with the usual sockets and supports (none or which is shown) to supply light. The smaller can be a 22 watt lamp, for example, and the larger a 32 watt lamp. Such types of lamps are commercially available at this time, and have generally the following characteristics:

The 22 watt lamp requires a starting voltage of about 118 volts; operates at a voltage of about 62 volts; and since line voltage is sufficient to ignite the same, it requires no transformation from line voltage. Suificient reactance can be obtained through the use of a simple inductive reactor such as a choke, to ballast the same after ignition. This would of course also be the cheapest expedient.

The 32 watt lamp requires a starting voltage of about starting voltage is greater than line voltage, some transformation is required to ignite the same, and obviously provision must be made for sutlicient reactance to ballast the same once it has become ignited.

Considering now Fig. 1 of the drawings, there is illustrated an electromagnetic device 16 embodying the invention. The core which is designated generally 15 is an important part of the electromagnetic device 16 which includes the windings to be described. Since same is known popularly as a ballast this designationwill, be used interchangeably throughout this specification and the claims.

The core 15 is formed of laminations punched from suitable electrical steel. There is an outer shell 17 having elongate side legs 18 and bridging ends 19, the laminations forming shell 17 preferably being integrally formed as single stampings. The shell 17 is held in assembly in any desirable manner. As shown, a suitable number of laminations are stacked and riveted together by rivets 20. In the center of the shell 17, the core The use of central winding leg.

and thewindow 35 on the opp'ositeside thereof. "viouslythe window'34 is defined by the extensions 24 and 25, and like the windows 28 and'35 is formed of equally shaped parts on opposite sides of the winding leg.

and held together by suitable rivets. 23. Economically,

the winding leg laminations are punched out of the center of the shell laminations at the time the shell laminations are being formed, this being done in one or. more oper-, ations. The laminations could be formed of longitudinally split halves and the whole clamped together, if

desired.

. The presence "of the shunt 2 7 provides a window 28 at the right hand end of the ballast core 15. Obviously the Window has two parts, one Ion -eaeh*side'oi the s for the extensions 25, these are provided-withinangular tips 30 which extend into appropriate notches T31'formed in the central Winding legthereat. It will be note'd that thetriangular tips iii) are formed'by reason of "the 'fact that the end faces "of tllCfiXtfilflSlOBSfZS are at an angle with respecttothe long dimension of the'windleg' 22. These faces engage the notches 3-1 andextend "into the winding leg 22 onaslant toward the right hand .end of the core 15. Thus there is a portion '32 of the 'rig'htihandedg eof each oftheextens'ions-25 that extends in'tothe winding leg atright'ang'lesto its'long dimension.

This construction prevents movement of the winding leg t'othe'left, but does not opposemovement'to'the'right;

The reasons therefor shortlywill be discussed.

Inasmuch as there is no gap between the respective exftens'ions 25'and the winding leg 22, there isformed at this I position a magneticshort' circuit 33 sinceth'ere'is no opposition to fiux passing directly from the extensions '25 to the winding leg 22 and 'vi'ce'versa.

T he presence of "the extensions 25 gives'ri'se to window 34 on the right side of the magnetic short circuit '33 'At"the left hand end of the-core 15, on "the inner surface of the bridging end 19 'there is a're'c'ess which'may l 'bcfor'rjned either by working the metal out of the side jface'f'of the .end 19, or 'by punching'same out during the of the respectiveIlaniinations. The'lefthand end of the leg'22 terminates just even with the normal inlner faceof the end .19 .and hence thereis formed a nonmagnetic gap37'at thispoint.

It will be secn marksman 1 magnetic connection -between'the"centralhwinding leg 22 at its .left end and the .shellf17, the said ivinding legfdepending for -support (mine connection between the extensions 25 an'dTthe notches .31. As for the right handfend ofthe winding i lcg 22,"'same is 'intimately and matingly engaged with a [suitable notch formedin' the righthand are 19 to'form thetightfjiincture "38. "The efficiency of the electroma "netic device 16 ca1ls for'this" juncture always to be "tight sd-It hat the passage of magnetic flux is inno way hindered The advantages of the notched connection of the maghome into-the shell 17' and accurately fixes the width -:of the gaps '26 "and 37. The second important advantage is that"any "strain caused' by magnetic flux- 'attempting to right. This is because the slanted end faces of the extensions present less resistance to movement to the right than the portions 32 present to the left. Movement to the right can do nothing more than more firmly seat the juncture 38, but because of the juncture such movement is practically impossible. There is a binding effect which -:dec,reas,,8 vib a o y o ses a jun tur 38- Since the portions 32 of the sides of the extensions 25 are at right angles to the long dimension of the'eehtral Winding'leg 22, movement to the left is impossihle and the Width of the gap 37 can be maintained with great accuracy. There is little tendencyfor spreadingofthe shell 17 in the center which might cause widening of the gaps 26, because the movement of the central winding leg 22 to the right must be quite marked in order for the extensions 25 to move outwardly any perceptible amount.

.In .theinterestsof preventing noise,,the left hand end of-the central winding leg 22 may be provided .with. a .small centrally located integrally formed teat or protuberance 40.adapted.to engage in a suitable notch in the bridging end 19. This provides thegap. 37 ,with .acentral support. vInFig. 4 this modification isshown, and there is :alsoshown a modified form of extensions 25' which do not have triangularly shaped ends but instead closelyabut against thesides of the central winding leg-to form themagnetic short :circuit 33. The physical support of both-endsof the central winding leg 22 decreases the necessity for using the expedient shown in Fig. ,1 to preventany possible movement of the central winding leg to the left.

A further modification of the extensions is shown in Fig 5. Here the'extensions 25" arerounded and extend "into notches- 31 of identical shape formed in the central winding leg. The left hand end is shown without supportsincethe magnetic short circuit is a rather rigid connection between shell and winding leg. The unequal resistance tomovementwhich is characteristic of the em- Llbodiinent of Figrlis not available by this construction.

The'circuit of the ballast is shown in Fig. 3 orFig, 6 in which,-in order to render the drawings more lucid, the lamps 10 and 11 have been-diagrammatically developed sothat they have the appearance of the conventional *usual iron core convention.

in proper relation to their actual physical location.

' The primary winding P is mounted in the central window 34,-with the secondaryrwinding S in the window 28 on the righthand end of the core 15 and the choke-windilig in the window'35 on the left hand end. In Fig.- 1

"the windings are shown in sectio'm and it-should beobvibus that they" surround the central windin'g leg 22 inthis particular l rind of core. Efficientproduction is preferably *ach-ieved by'pre-forming the respective winding'skmounting them upon'the central 1 winding leg in proper position "and relation one tothe'other, and then forcing the assem- I -bled-center into'the shell 17.

*Examining the circuit of the device 16 shown in Fig. -3,

We see that the lamps 10 and 11 are each shunted by a "conventional starter switchSt for causing ignition thereof. The lamp 10, which is the smaller of the-two is' co nnected in series with the choke winding Ch; and "together 'with the choke winding"connectedf 'across the primary P. Winding Ch is in'-lead 40 'which connects -withri'ght side of primarywinding P. -L'ead"41fco'rinects with lead 42whi ch connects with'left side of primary P.

(The primary winding "P --is energized from aconventional =line and has terminal leads 44 arid- 45 to permit such'c'onnection. F or the examples; described the WilLbe a 11 8 volt, 60 cycle A. power sourcef' The second winding S is connectedinauto-transfor1ner relation-to the primary winding P, and its left hand'terminal is connected by lead 46 to the rightsideof-the Ipriget er 1 P, while its right hand terminal connects by lead 47 to the larger lamp 11. Lead 48 connects left end of lamp 11 to common conductor 42 and through the same to the primary winding P.

Since there is a magnetic short circuit 33 between winding Ch and the rest of device 16, when the primary winding P is energized, no flux will affect winding Ch. Until lamp ignites no current flows through Ch, and the only voltage to which lamp 10 is subjected is 118 volts from the primary. We may disregard the starting circuit with switch S and the initial minute flow of current for heating up the filaments. Note that the winding Ch and the surrounding portions of the core 15 together with gap 37 form a high inductance choke. This choke functions after the lamp 10 is ignited, serving to limit current flow therethrough.

The energizing of the primary winding P, however, in duces a voltage in winding S, since same are magnetically coupled, so that the ignition voltage across the lamp 11 during starting is the sum of voltages of P and S. Loose coupling between P and S provides high leakage reactance after current flows so that the winding S serves to ballast lamp 11 and limit current flow therethrough.

It will be seen that this construction provides a ballast for operating two gaseous discharge devices having different characteristics in which ballast there are achieved considerable savings in both material and labor. Only one article is to be produced and handled, and the volume occupied is considerably less than it would be were two electromagnetic units used.

The construction which has been described is novel in another manner which gives rise to great savings. The outline of the laminations illustrated in Fig. 1 is exactly proportional to the dimensions of an actual commercially produced example of the device. The overall length of the shell 17 was exactly five inches, and the ballast was intended for igniting and operating the lamps whose characteristics have been set forth herein. With this device, it will be seen that the width of the extensions 24 is about one-half inch, and the width of the extensions 25 is about one-third of an inch. This latter dimension is surprising, since theoretically, the flux which is produced during operation by both the primary P and the choke winding Ch will thread the magnetic short circuit 33. This concentration of flux will tend to saturate the core at this point and distort the wave shape. Good engineering would dictate a width of the extensions 25 of more than twice that shown.

We have found that the width of the extensions 25 can be made quite small without in any way afiecting the core saturation by the expedient of arranging the windings P and Ch so that their respective fluxes are in phase. This is done by connecting the windings appropriately in a manner well known in the art. The

flux arrows in Fig. 1 show the principal flux FL of the choke winding Ch pointed to the right and splitting at the magnetic short circuit 33 with the flux threading the short circuit passing outwardly of the central winding leg 22. The primary flux Fp is shown directed inwardly of the central winding leg and joining at the center thereof to form the arrow directed to the right. Obviously the primary and choke fluxes while in phase through the central winding leg are in opposition in the extensions 25. The resultant fiux density will therefore be considerably smaller through the magnetic short circuit than if the flux patterns were arranged to enforce instead of buck one another.

Although there is no magnetic relation required between the right and left hand parts of the ballast, the existence of the relation described gives rise to many advantages we have enumerated. Furthermore, notwithstanding the decrease in the size of the extensions 25, other constructional features have been pointed out which are considered of importance.

Measurements made in the commercial version of the 6 invention relative to flux density show that the theory set forth above is probably a valid explanation of what occurs in the core. A table of such measurements has been set forth below giving the flux density in Gauss in various parts of the core under different circumstances.

A B C D Both lamps operating 12,400 6,280 10,000 10,700 Lamp 10 off 12, 400 13,850 500 Lamp 11 ofi 83 7, 540 10, 000 10, 400

In the above table, the places at which the measurements were taken are marked in Fig. 1. A represents flux passing through the shunt 27, B represents flux threading the short circuit 33, C represents flux in the outer arm of the choke core, and D represents total choke flux. Flux density approaching saturation is of the order of 18,000 Gauss, and it will be seen from the table that this is never reached in the ballast. The most significant part of this table is column B. Note that when only the lamp 10 is operating the flux density in the extensions 25 is 7,540 Gauss. When only the lamp 11'is operating the fiux density at the same place is 13,850 Gauss. When both lamps are operating, the resultant flux density in the extensions 25 is the diflerence instead of the sum of the fluxes produced by the two parts of the device, and hence the extensions can be made very narrow.

The dimensions of the example discussed can be obtained by simple proportions from the single dimension given that the length of the lamination of Fig. 1 is five inches. The lamination was formed of ordinary electrical steel of a gauge usual for such size ballasts, and the stack was three quarters of an inch high. The choke winding Ch and the secondary winding S were each formed of 740 turns of No. 27 /2 wire. In the design of a ballast of this type, the inductance of the winding S must be sufficient to ballast the particular lamp 11 used. In the specific example, the number of turns necessary to supply the desired secondary inductance in the event the entire primary is used as a source of starting voltage would subject the lamp 11 to too great a starting voltage. Hence, only a part of the primary was used for supplying starting voltage as shown in the modified circuit, Fig. 6. The left hand end of the secondaryS, instead of being connected by way of lead 46 to the right hand end of the primary P and joining the terminal lead 45 thereat, was instead tapped in some windings short of the end, as for example by the lead 46', there being no other connection of the left end of S to the primary P under such circumstances. The primary winding P in this case was formed of 750 turns of No. 30 wire and turns of No. 27 Wire, with the secondary winding S tapped in at the junction of the two partsof the primary. Obviously the heavier wire isrequired since all current passes through the smaller section of .theprimary.

It is desired to point out that the specific proportions and dimensions used are capable of wide variation for the purpose of adapting the invention to use with other types of. gaseous discharge devices. In the case of certain advantages of the inventi0n, the configuration of the core as set forth need not be followed, and in other cases, different variations are possible without departing from the spirit of the invention.

What we desire to secure by Letters Patent of the United States is:

1. In a ballast of the character described and including a single unitary core having an outer shell and a central winding leg, said central winding leg terminating short of the shell end at one end of the said leg thereat a non-magnetic gap and engaged intimately with the shell at the second end thereof, a pair of aligned extensions of the sides of the shell integrally formed therewith and engaging againstthe central winding leg from i -oppe site si'clefsbther eof tbetween said ends and forming thereby 1 a magnetic iShOI't circuitseparating tile core-into WO parts; a -wiriding=rnonnted on the; central-winding leg in -the part having ;the saidegapeandadapted" to serve as -a choke-winding and a-pair of-windings mounted on the -central--winding leg inthe second part and" adapted to serve as a transformer, and means for preventing longi- --tudinalmoyement of-the; central-windingdeg from--va1'yling thetgap at said first end..comprisinganotches :formed in the s aid winding leg and having the ends ofgthe said extensio wneeee vtl .csa wtwtclle sa notch -v,be ?snubs: eat -E pen-symme ical iv-shaped "w t the si s ot n neqnall, length iand having the ends of theexnttpn tsloa xw n a 2 In a ballast ,of the chat acter described and including a sinqle nnitarycore haying anouter shell and. a cen- 'n e el e ssni e Win l, lee/terminate}; sshq tn l the sa sm to e en l etheai -l e h r a n9n magnetic; gap and engaged intimately with the hell, at the second end thereof, apair, of L aligned exten- ,,.s, qns of; thes de to he. h t ntssta yf medtther wi and engaging against ,the central. winding. leg irom opqsite, sides thereof 1 between said .,endsand, v forming thereby agnagnetic short circuit separatingflhe core into two p arts, a-. winding mounted on the central winding z leg in the part hayilglgw the said gag and adapted toserve wa ascht ket indi sx a Pa t o tw n in m u tedb the central winding leg in the second part and .adapted to serve as a transformer, and means fpr preventing gitn dinal rnoyement ,of thewcentral,windirigdegfrom ya'rying the gap at s aid first end comprising notches formed in the ,said winding leg and; ha ving {the ends .of the aid extensions engaged in the said notches, said I e en sion ends haying their, faces fqrmed on a plane slanted inward of the central winding leg in a direotion toward the second end of thetwinding leg whereby the sides of the-said extensions will be of: unequal; length )with ihe lonyer side extending substantially into the winding leg to oppose movement of thefleg tending to .sle e th s p- 35in aballastcf the character described and including a single unitary core having an outer shellandra ceni tial winding leg said central winding leg terminating shortioflthe shell end at oneendof the said leg thereat a non-magnetic gap andengagedintirnately with the, shell at the '.second end thereofita pair of aligned extensions 'of the sides ofi theshell integrally formed therewith and en aging against the 'central. winding leg from opposite 'sides thereof between saidendsland forming ithereby a magnetic short circuit separating the core into two parts, a winding monnted on the central winding ,legin theepart haying the said gap and adapted to. servetas a choke winding, and a pair pf windings mounted on the central winding legjn the second gart and adapted,to serve as a transformer, and means for preventing longitudinal m o vement of the central winding 'leg from vgi'rying, -the gap at said 'first end comprising notches formed jn the said winding leg and haying the ends of the said ex- I tensions engaged in the said notches, said extensionends haying theirfaces formed on aplane slanted inward .of the central winding legv in afdirectiqn l w fd the second en Qf th W din v le whereby th sid l tthes i tensigns will be of unequal lengthwithi-the longer side extending substantially into the winding leg to oppose y mbvement of the legtendingtqglose the gap;'"the second e-{side of eacheextensiens interseeting*theiplanesubstantially at the edge of the central winding-- leg so that resistance to lengthwise movement of the central windingdeg-stowards theseeondq endwill -be' less than the/resistance in ijihG QPPQSiIC-QiiICfiQfi Ofinovemfint. t

- 4. '{In-combination;'a pair of 'gaseousdischarge devices of idiiferent starting -and; e teratinge characteristics; a 10 source of A C. pdw1';0fsuflicient wolatge-to 'igniteone dev-iee -but ins nfieient-to ignite the second device and a ballast+for supplying eurrent to the devicesf from said -sonrce---comprisingan elongateouter shelland a c'en- -tral winding leg, aeprimary windingg a-secdz1'dary wind- -ing and a-ichoke -windingtall mountedonethe winding leg, the--cheke winding being connected-imgeries witht the one device and together thereWi-th connectedaerqssthe primary the primary aridsecondary-windings' being con- =nectedk-in antot-ran'sformen-relationship -with-fthe second l device, ;said-shiell-' having e a pail-of -extensions-tin tegral --with opposite 'longfsidesj thereof-and; terminating against -the -centralwinding; leg'-to}-form -a -magnet-ic short' circuit 'therebetween, thechoke' and-primary-'=wind ings being positioned on-opposite sideseti the-' extensions 'and their voltage ---senses '-=being additive -during operation of the gaseous "discharge devices to produce-flux; travelling fthrough-the central winding leg in the same directiom'but 1 through-the extensions f in -obposite 1 directions such that the fiux density -in' the 'short circnitiwill' be" considerably less' than the sum of -flux de'nsitiesfine to-the-respective windings considered separately, said primary winding -having leadsconn'eeting same to;said' sourcef the central w-inding leg having one endengaging the shell in closed t magnetic circuitrelationat "the ,end adjacent the "secondary winding and having :the opposite end spaced rpm the (shell to form-an air A gati adjacentfthe 1 ehgke winding. V

1 5. v A construction "as" described; in claim ".4 "inwhich said-shell" has asecond pail- 0f extensions integral with opposite long; sides rthe reof po'sitioned between the" primary-andsecondarywindings -and;each'terminatingshort -of-*the-;winding'- ;leg to provide amen-magnetic air gap --thereat,-; whereby to provide loose; couplingibetween the primary and; secondary;;windings and;high==leakage reactance for ballasting said second 'deviceduringfgperation thereof. 1

- 6. A'constrn ctipn as described in claim- SinWhich-f'the extensions-between said primary j and choke" windings are engaged in notches provided in said .centralwinding 0 ieg'to ni'eventlengthwise movement of said center winding leg.

t France -Inly' 28,' 1.947 

